Contents lists available at ScienceDirect Environmental Research journal homepage: www.elsevier.com/locate/envres Usefulness of toxicological validation of VOCs catalytic degradation by air- liquid interface exposure system Margueritta Al Zallouha, Yann Landkocz, Julien Brunet, Renaud Cousin, Eric Genty, Dominique Courcot, Stéphane Siffert, Pirouz Shirali, Sylvain Billet ⁎ Unité de Chimie Environnementale et Interactions sur le Vivant EA4492, Université du Littoral Côte d′Opale, 189 A Avenue Maurice Schumann, 59140 Dunkerque, France ARTICLE INFO Keywords: Catalytic oxidation Air-liquid interface exposure Toluene Toxicological validation By-products identification ABSTRACT Toluene is one of the most used Volatile Organic Compounds (VOCs) in the industry despite its major health impacts. Catalytic oxidation represents an efficient remediation technique in order to reduce its emission directly at the source, but it can release by-products. To complete the classical performance assessment using dedicated analytical chemistry methods, we propose to perform an untargeted toxicological validation on two efficient catalysts. Using biological system allows integrating synergy and antagonism in toxic effects of emitted VOCs and by-products, often described in case of multi-exposure condition. Catalysts Pd/α-Al 2 O 3 and Pd/γ- Al 2 O 3 developed for the oxidation of toluene were both coupled to a Vitrocell ® Air-Liquid Interface (ALI) system, for exposure of human A549 lung cells during 1 h to toluene or to catalysts exhaust before quantification of xenobiotics metabolizing enzymes. This study validated initially the Vitrocell ® as an innovative, direct and dynamic model of ALI exposure in the assessment of the performances of new catalysts, showing the presence of chemically undetected by-products. The comparison of the two catalysts showed then that fewer organic compounds metabolizing genes were induced by Pd/γ-Al 2 O 3 in comparison to Pd/α-Al 2 O 3 , suggesting that Pd/γ-Al 2 O 3 is more efficient for toluene total oxidation from a toxicological point of view. 1. Introduction Volatile Organic Compounds (VOCs) represent a variety of sub- stances belonging to different chemical families (aromatic hydrocar- bons, ketones, alcohols, alkanes, aldehydes, etc.) and known for being important contributors to air pollution (Khan and Ghoshal, 2000). Among the major VOCs, Benzene, Toluene, Ethylbenzene and Xylenes (BTEX) have major and direct impact on human health. Toluene is widely used in many industrial sectors where 32% of commercial toluene enter in the process of benzene synthesis and 19% is used as solvents with almost 90 kt/year as paint solvents in European Union (Hansen et al., 2002). Toluene has a relatively well known toxicity with the respiratory tract as major route of absorption. Limit values for occupational exposure to toluene were established in France, in 2012, with an exposure limit value of 20 ppm equivalent to 76.8 mg/m 3 for 8 h and 100 ppm (384 mg/m 3 ) on a short-term (under 15 min). The same values were set for the 8 h exposure in the USA since 2007 (INRS, 2012). After absorption, toluene is primarily metabolized in the liver, where 80% of the absorbed dose undergoes a chain of oxidation reactions by the intervention of different enzymes which make the molecule more hydrophilic and allow urine excretion of metabolites. Between 10% and 20% of inhaled toluene are excreted in the expired air with a half-life of about 25 min (Benoit et al., 1985). Toluene is known for both acute and chronic toxic effects (Tormoehlen et al., 2014). It is classified as a Carcinogenic, Mutagenic and Reprotoxic (CMR) category 3 due to its toxicity for reproduction. Because of toluene toxicity, it is necessary to reduce emissions directly at source. When substitution is not possible, catalytic oxidation represents an economical and environmental alternative to the thermal oxidation of VOCs. The choice of suitable catalysts for the total oxidation of toluene should usually take into account the activity, stability, cost and feasibility of large scaling-up of laboratory systems. A catalyst is generally formed by a support and an active surface. Aluminium oxides, especially α-Al 2 O 3 and γ-Al 2 O 3, present good performances as supports for active phases for BTEX oxidation. Aluminas have some interesting properties like a high thermal stability for α-Al 2 O 3 or a high specific surface area with acidic properties for γ- http://dx.doi.org/10.1016/j.envres.2016.10.027 Received 22 July 2016; Received in revised form 24 October 2016; Accepted 27 October 2016 ⁎ Corresponding author. E-mail address: Sylvain.Billet@univ-littoral.fr (S. Billet). Environmental Research 152 (2017) 328–335 0013-9351/ © 2016 Published by Elsevier Inc. Available online 09 November 2016 crossmark